Patients can be severely injured when fluids that are intended for intravenous delivery are delivered outside a targeted vein. Possible consequences of prolonged delivery of an infused fluid outside the targeted vein include irritation, tissue necrosis, compartment syndrome, disfigurement, loss of limb function, amputation, and even death of the patient. Extravasation occurs when the outlet of a cannula is misplaced or becomes dislodged to a region outside the vein. Extravasation refers herein to improper placement or movement of the outlet of an intravenous cannula to a region outside the targeted vein, or delivery of a fluid that is intended for intravenous delivery outside the targeted vein.
Various methods are known to the art for detecting extravasation in an infusion system. Such tests can be employed for minimizing delivery, outside a targeted vein, of fluids intended for delivery within the targeted vein. If extravasation is detected, then the flow of delivered fluid can be stopped when the faulty condition becomes known.
In one method of detecting the proper placement of a cannula during an infusion, the DC component of the pressure is monitored in an infusion line. Proper placement of the cannula in a vein is detected when the pressure in the infusion line tracks the DC component of the pressure in the vein. Extravasation is determined to have occurred if the monitored pressure occurs outside a prescribed pressure range. However, this method suffers from the possibility of failure to detect extravasation, because an apparently proper pressure can be produced while the cannula is outside the vein, resulting in significant accumulation of extravasated fluid and possible injury when the infusion is continued under the undetected faulty condition. Furthermore, the DC pressure method requires sophisticated electronics, which may be unavailable in some emergency situations such as accident sites and battlefields, unavailable at severely budget-constrained clinics, or which may be unsuitable for flowing vesicant or cytotoxic medicines, for very low flow applications, or for any other applications in which it is preferred not to use a powerhead for infusing a fluid. A powerhead is a powered pump that positively actuates forced delivery in an infusion line.
Another extravasation detection method uses the AC component of the vein pressure. Both veins and arteries have a pulsing AC pressure component. The AC pressure component can be detected as either a variation in pressure or a variation in flow in an infusion line, according to U.S. Patent Application Publication No. 2007/0112329. The pulsing AC pressure is detected in the infusion line if the cannula is properly placed in the vein, and not detected if extravasation has occurred. If a pulse is not detected for a few seconds at any time after the start of an infusion, then extravasation is determined to have occurred. However, like the DC pressure method, the AC pressure method requires sophisticated electronics which may be unavailable or unsuitable for the same above listed reasons.
Numerous references disclose extravasation detection with infrared, RF, microwaves, ultrasound, light, pressure response to a test injection, or changes in temperature. These methods require sophisticated electronics and many of them involve probes which are applied separately from the infusion line. Extravasation is inferred from a measured change that is a secondary consequence of accumulation of extravasated fluid. Assumptions are made and relied upon as to how tissue properties will change when a delivered fluid accumulates outside a vein, and significant quantities of extravasated fluid may accumulate as the infusion is continued under an undetected faulty condition if these assumptions fail.
U.S. Patent Application Publication No. 2013/0310743 discloses a test that detects extravasation by monitoring for entry of blood near the cannula when the flow of delivered fluid is momentarily reversed by a finger-type powerhead. However, in some applications, it is preferred not to use a powerhead, such as for intravenous delivery of vesicant or cytotoxic medicines, for medicines that are delivered at a very low flow rate, or for any other medicine or circumstance in which forced delivery of the medicine is contraindicated.
In one commonly used extravasation test, an infusion line is backflowed with a syringe. A syringe is connected in flow communication with the infusion line between a puncture site and a point in the infusion line at which the flow has been restricted or shut off. Proper placement of the cannula is detected if blood flows back into the infusion line from the puncture site when the syringe's plunger is pulled back. This method requires the syringe or other extra equipment not already present on the infusion line, which must be supplied for performing the test. Repeated testing with this method consumes many syringes, the total of which may be expensive, and the test itself requires significant effort to perform, all of which present a deterrent of using this method to check or monitor proper placement of the cannula. Furthermore, concerns are raised about sterility when a syringe or other additional equipment is placed in flow communication with an infusion line.
“Roller clamps” have been used for throttling the flow in an infusion line. The roller clamps shown in U.S. Pat. Nos. 6,422,529 and 8,313,081 have a wheel that pinches an infusion line against a bottom wall having a relief groove in order to throttle an adjustable, nonzero flow throughout the substantial length of the wheel's range of travel. The roller clamps shown in U.S. Pat. Nos. 6,422,529 and 8,313,081 do not aim to pinch the infusion line fully closed and then peristaltically withdraw fluid back into the infusion line by movement of the point of closure.
Based on the forgoing, there is a need for an extravasation tester that pinches an infusion line closed between a wheel and a platen, and then peristaltically withdraws fluid into the infusion line as the wheel is rolled away from a puncture site. Extravasation is determined to have occurred if little or no blood appears in a sight chamber near the puncture site when fluid is withdrawn into the infusion line from the puncture site.